Acoustic wave device, module having the same

Abstract

An acoustic wave device includes a substrate, a transmission filter formed on the substrate, a reception filter formed on the substrate, a transmission ground pad of the transmission filter, the transmission ground pad is formed on the substrate, and a reception ground pad of the reception filter, the reception ground pad is formed on the substrate. The transmission filter includes a plurality of series resonators and a plurality of parallel resonators. The plurality of parallel resonators includes a first parallel resonator electrically connected to the reception ground pad.

The invention claimed is: 
     
       1. An acoustic wave device, comprising:
 a substrate; 
 a transmission filter formed on the substrate; 
 a reception filter formed on the substrate; 
 a transmission ground pad of the transmission filter, the transmission ground pad is formed on the substrate; and 
 a reception ground pad of the reception filter, the reception ground pad is formed on the substrate, wherein 
 the transmission filter includes a plurality of series resonators and a plurality of parallel resonators, 
 the plurality of parallel resonators includes a first parallel resonator electrically connected to the reception ground pad, 
 the plurality of parallel resonators includes a second parallel resonator electrically connected to the transmission ground pad, and 
 the first parallel resonator and the second parallel resonator are resonators divided in a final stage of the transmission filter, the final stage is disposed at a position farthest from an input terminal of the transmission filter among the plurality of parallel resonators. 
 
     
     
       2. The acoustic wave device according to  claim 1 , wherein the first parallel resonator is not electrically connected to the transmission ground pad. 
     
     
       3. The acoustic wave device according to  claim 1 , wherein a capacitance of the first parallel resonator is less than an average value of capacitances of the plurality of parallel resonators. 
     
     
       4. The acoustic wave device according to  claim 1 , wherein a capacitance of the first parallel resonator is the smallest capacitance of the plurality of parallel resonators. 
     
     
       5. The acoustic wave device according to  claim 1 , wherein the first parallel resonator has a resonant frequency that approximates a frequency of the highest frequency of the passband of the reception filter. 
     
     
       6. The acoustic wave device according to  claim 1 , wherein the substrate is a substrate in which a piezoelectric substrate and a substrate made of sapphire, silicon, alumina, spinel, quartz, or glass are bonded to each other. 
     
     
       7. The acoustic wave device according to  claim 1 , comprising a transmission ground electrode electrically connected to the transmission ground pad, and a reception ground electrode electrically connected to the reception ground pad, wherein an area of the reception ground electrode is larger than an area of the transmission ground electrode. 
     
     
       8. A module comprising the acoustic wave device according to  claim 1 .